Gear grinding machine



Sept. 12, 1950 A. AEPPLI GEAR-GRINDING MACHINE s Sheets-Sheet 1 Filed Aug. 23, 1949 FIG.

Sept. 12, 1950 A. AEPPLI GEAR-GRINDING MACHINE 6 Sheets-Sheet 2 Filed Aug. 23, 1949 FIG. lo.

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Sept. 12, 1950 A. AEPPLI GEAR-GRINDING MACHINE 6 Sheets-Sheet 3 Filed Aug. 23, 1949 FIG. 2.

Sept. 12, 1950. A. AEPPLI GEAR-GRINDING MACHINE 6 Sheets-Sheet 4 Filed Aug. 25, 1949 2a. F/G. 2a.

Sept. 12, 1950 A. AEPPLI GEAR-GRINDING MACHINE 6 Sheets-Sheet 5 Filed Aug. 25, 1949 Sept. 12, 1950 A. AEPPLI GEAR-GRINDING MACHINE Filed Aug. 23, 1949 r Patented Sept; 12, 1950 UNITED STATES PATENT OFFICE I I I I 2,522,334

GEAR GBINDINGMACHINE Albert Aeppli, Zurich, Switzerland, assignor to Maag Zahnradernnd-Maschinen, .A. 6., Zurich, Switzerland, a company of Switzerland Application August 23, 1949, Serial'No. 111,840

' In Great'Britain August 24,1948

19 Claims. 1

This invention relates to machines forgrinding the tooth flanks of gear wheels.

It'is already known to grind the tooth flanks-f externally toothed gear wheels by an involute -generatingprocessinvolving the use of two grinding wheels, one for each side of a tooth or of "two teeth;

Such machine, however, are not generally suitable for grinding the tooth flanks of internally toothed gear wheels, because the space within the annulus of sucha gear is too restricted to accommodate two grinding wheels and to allow for the necessary-movementsthereof. Moreover, as :the tooth flanks 'of internally toothed gears with teeth-of involute form are concave it is not possible to use a grinding wheel of which the working part is a plane surface, as-is the casein known machines for grinding externally toothed gears. 'Inits place agrinding wheel is employed having an operative rim which makes substantially point-contact with the :tooth flank.

The object of =thisinvention is to provide-an improved-machine by which thegrinding'of internally toothed gear wheels, including those withinclined-or helical teeth,:can be efiicaciously carried outand which, atthesame time, retains most oi-theadvantages of the known gear-grinw v=ing machines above referred to.

According to the present invention, a single grindingwheel is provided .forgrinding the tooth fla'nks ofinternally toothed-gears by-an involute generating process, such grinding wheel being mounted for pivotal movement about an axis whichis perpendicular to, but .does not-intersect, the grinding .wheelaxis in such a way that, by pivotinguthe grinding wheel through approxi .mately.180, it.:canbe broughtiintoposition for grinding the other side of the teeth as well.

For grinding the flanks of closely pitched 1 nternal teeth, the-gaps betweenwhich-are accordingly small, it is necessary ior the rim of the grinding wheel to be correspondingly narrow. In order to strengthen the grinding wheel it is usually made dished or saucer-shaped. This -means, oicourse thatthe grinding wheel'always operates with the :same edge-or'rim, but by-mak- -.ing it carryout a pivotal: movement in-accor'dance --with this invention, the workingedge or rim can bet-made to faceeither way-and hence to er-ind both sides .oi .the teeth.

'According toa further feature of the-invet'ion, rtnerelation between the grinding wheel: axisand "the-axis.:.aboutzwhichz it is adapted to-pivot-may .be such that, .after pivoting through about 180 --theuworkinga point'of the grinding-wheel, which in operation lies on the base circle of the gear whejeLisinitiallysituated too high for proper operation, -namelywe11 above the base circle, and the grinding wheel is mounted for free vertical sliding movementbetween adjustable stops relatively to the axis about which it pivots so that immediately-after the pivotal movement, itdrops by gravity back -'to the correct position, deter,-

mined by the stops, with its working point on the basecircle of the gear being ground.

This-arrangement makes it possible, by adjustment-of :thestopa to allow for the use on the same machine of grinding Wheels of differentdiameters and :for reduction-in diameter by wear orv by a cutting,ldevicesuch as is usually provided iorthis purpose in .order to renew the operative edge or ri-m of the grinding wheel.

)A lateralor-horizontal adjustment of the grind- --ing wheel may also be provided for in order to compensate for wear of the operative rim at the side-thereof and forthe aotion of a lateral dressingdevice which is usually incorporated. For this purpose, themachine incorporates a feeler device-of a kind: known per se, which is kept inengagementwith-the side of the rim and which automatically brings about the said lateral adjustment .of'the grinding -wheel as the thickness "thereof-attherimis reduced either by wear or aiterithe dressingdevice has been in usebetween grinding operations. 'This lateral adjustmentis preferably obtained :by mounting the grinding wheel on :a tool-holder which in turn is carried tbyraeslideiina manner permittinghorizontal adiustment of thetool-holder with respect thereto under the-automatic action of the feelerdevice, :the slide-being mounted, for vertical movement betw-een the aforementioned stops, on a' turn- :table rotatable about the aforementioned pivotal axis.

-It'-wil1-'be-seen that-if the stops are adjusted when -a -reduction in diameter of the grinding wheel hasoccur-red the device for turningthe grinding wheel down-to reduced diameter and'the "feeler-devicewill 'require to be advanced towards the-centre of-the grindingwheel. According to a'f'urther'featureoi this inventi on, provision may bemade-whereby=both these devices are adjustably mounted andtheir means of adjustment are --coupled-with--the-means tor-adjusting the stops in sueh' a -manner that, when-fthe stops are ad- --ju 'stcd, the two devices are automatically advancedby a like amount.

a Preferablm-the machine is so arranged-'that-the grinding wheel snakes -no --movement in space -while--agrinding.operation is in progress (1. e.

apart from the adjustments mentioned in the foregoing), its working point remaining stationary upon the base circle of the gear being ground, whereas the latter is fed forward towards the grinding wheel whilst at the same time executing an oscillatory true rolling motion which is necessary for grinding the teeth to involute form and which is constituted by a combined rotary and lateral reciprocating motion.

In order to enable the invention to be readily carried into effect, one embodiment thereof will now be described by way of example with reference to the accompanying drawings. This description will also make apparent other features of the invention and the application thereto of the advantageous features of known machines, including those which enable both straight and inclined or helical teeth to be ground by an involute generating process.

In the accompanying drawings:

Figs. 1 and la, viewed together, constitute a side elevation of a form of gear grinder embodying the invention, certain parts being shown in vertical longitudinal section;

Figs. 2 and 2a, viewed together, constitute a top plan of this form of gear grinding machine showing certain parts thereof, particularly of the grinding wheel mounting and adjusting apparahis in horizontal section;

Fig. 3 is an end view of the top part of the machine viewed from the left of Figs. 1, 1a, 2 and 2a showing the apparatus for imparting the rolling motion to the work;

Fig. 4 is an elevation in vertical transverse sec tion of the grinding wheel mounting and adjusting apparatus only, the section being taken approximately on the line IVIV of Fig. la, though certain parts on the left of the section line of Fig. la are also indicated in Fig. 4 for a better understanding Fig. 5 is an end elevation of the grinding wheel mounting and adjusting apparatus only, viewed from the right of Figs. 1a and 2a, the parts designated by reference numerals 2, 3 and 4 in Figs. 1a and 2a (as well as parts associated therewith) being omitted in Fig. 5.

The form of machine shown in the drawings comprises a bed I (Figs. 1-3) on which is displaceable in the direction of the longitudinal axis B of the machine a lower slide 48 having an upper slide 4! mounted thereon displaceable transversely of the axis B. The upper slide 41 carries a rotatable work-holder 45 which is adapted to have fixed thereon the internally toothed gear 30 to be ground. Also mounted for rotation on the slide 41 is a shaft 46 which is co-axial with the tool-holder 45 and is connected thereto through the intermediary of a dividing or indexing device which, being of known construction and function, has not been indicated in the drawings, nor is any description thereof thought necessary. Mounted on the shaft 46 is a rolling are 49 (in the form of a cylinder or part of a cylinder shell or, as shown, a segment of a cylinder) of a diameter corresponding to the base circle diameter of the gear being ground. Connected to the circumference of this rolling are 49, at opposite sides thereof, are flexible steel tapes 50, the other ends of which are fastened to levers 5i pivoted to a frame 52 mounted on the lower slide 48. The slide 48 is driven to make a feed movement towards the grinding tool E3 (to which detailed reference will be made hereinafter), and it is adapted, through a crank drive 54 mounted on the slide 48, to reciprocate the upper slide 41 perpendicularly to its own movement. The steel tapes 50, being held by the frame 52 which. does not take part in this reciprocating movement, roll on and off the rolling are 49 and cause the latter to rotate as it traverses across the machine with the upper slide, thereby imparting to the gear 30 being ground a true rolling motion relatively to the grinding tool .13 so that the latter, when in contact with a tooth of the gear 30, grinds the tooth flank to involute form. The grinding wheel 13 does not move in space during this operation, and its point of contact with the tooth flank is and remains in a plane passing through the steel tapes 50. The latter, being tangential to the rolling arc 49 and, hence, to the base circle of the gear being ground, represent in concrete form the line known as line of action of the gear being ground. The drive ratios are so chosen that, during a slow feed motion of the lower slide 48, many traversing motions of the upper slide 47 take place. The dividing or indexing device previously referred to periodically causes the gear 30 to be rotated (without rolling) so as to bring another tooth flank up against the tool I3.

In many cases, it is of advantage so to grind the tooth flanks that their portions near the tip and/or root of each tooth are rounded 01f, i. e. deviate slightly from the true involute form at these places, because this gives better performance in the use of two mating gears which are under a particularly heavy load. This is dealt with in co-pending U. S. application Serial No. 69,273 filed January 5, 1949 and issued as Patent No. 2,486,020 on October 25, 1949 which discloses means for bringing about such localised deviations from the involute tooth form. Similar means are also incorporated in the present embodiment, and a detailed description thereof is considered unnecessary. It will suffice to point out with reference to Fig. 3 that the tape-holding levers 5! have tape-tensioning screws 56 mounted therein which bear on movable elements 51 mounted in the frame 52. In response to actuation by the means above referred to and not described herein, the elements 51 jointly make a small movement to the left or to the right as viewed in Fig. 3, at the very moment when the tool I3 is grinding a tip or a root portion of a tooth flank, thereby pivoting the levers 5| in unison and imparting, through the tapes 50, a small rotary motion to the rolling are 49 additional to its rotary motion obtained by its reciprocation relatively to the tapes, such additional rotary motion being of course transmitted to the work 30 at those moments and causing the tool to take off a little extra material at those places and thereby to produce the desired rounding off, whilst at other times the levers 5| do not move relatively to the frame 52 so that the remainder of the tooth flank is ground to true involute shape.

The grinding wheel and its manner of mounting, operation and adjustment will now be described.

Referring flrst to Figs. 1, 1a, 2 and 2a, the machine bed I has mounted thereon a frame structure in the form of a standard 2 which can be turned about a vertical axis C with respect to the bed I by means of a pivot pin 55. A slide 3 is carried by the standard 2 and is vertically displaceable thereon by means of a screw spindle 4 operated by a hand wheel. A second slide 5 is mounted on the slide 3 for horizontal adjustment with respect thereto, preferably by hydraulic or pneumatic means to be described hereinafter. Theslide 5 carries a turn-table 8 which is rotatmasses able thereon about an aids A (Figs! and 5) means of a pin l on the ttnn-tahle 6 journal-led in a bearing in the slide 5. Rotation ofthe turn-- table is effected manually or automatically by means of a worm gearing 8, the 'Worn' whe'el "being formed on a circular flange oi the turn-table (Fig. 1a). Mounted on the latter is a further slide 10 which is vertically movable with respect to the turn-tahle "6, being guided in linear ball 'bear ings 'l'l provided therebetweeniFigs. 2a. and 5"). The slide F0 carries a tool hoider 12 which "is horizontally adjustable with respect thereto. The tool holder 12 supports, and provides the hearing for rotation of, the grinding wheel (hand in addition it-suppcr'ts "a motor 1-4 for driving the grinding wheel by means of a belt 15.

Horizontal adjustment of the tool lrolder 1 2 along the slide in is automatic for the purpose of ensuring thatthe tool is at all times during the grinding operation maintained in proper working position with respect to the work. Thus, if the working rim of the grinding wheel 13 should becoine worn down, the toolho'l'd'er is automatically moved closer to the work by acorrespondin'g distance. Devices for efiecting such adjustment are already known, for "example from SJ'PatEIit No. 1,228,798 which may "be referred to for furthere details. For the purpose of an'understan'ding of this embodiment of the present invention,

it will be su fiicient to polnt out that a feeler 1"6 ment through two pairs of bevelgears 24 and 25 respectively, to an eccentric 2B which operates apawl 1! (see Figs. l-a andA) to'rotate 'a'ratchet wheel is through 'an 'a'n'gle corresponding to one tooth thereof *per revolution oftl re eccentric T6. The rotation of the ratchet wheel 18 is "transmitted, via gearing 19, '20, to a screwed spindle 2| (Fig. 2a) which is engaged by am'zt secured to the tool-holder. 1'2 and thereby effects the horizontal movement thereof relatively to the [slide l0 against the action of a spring 22 "which prevents overrunn-ing of the device by ensuring that the horizontal adjustment "of the tool-holder stops soon as the i-mpuise given by the Tee'ler 16 ceases.

The tool-holder F2 is guided in its'horizontal movement by linear ball-bearings '2'3 (Fig Ia and'). V

There is only one grinding "wheel f3,antl "it dished or saucer-shaped. It works within, and with its upper rim in contact with a tooth flank near the to of, the annulus or the internal gear being ground (such as The rim only makes point-contact with the tooth flank, or to be more precise, only a verysmall area of the rim contacts the tooth flank. I

As the internal gear 30, while being 'slowly'fe'd forward towards the grinding wheel I 3 "by the "feed sheets, is osoillatedback and forth with a true rollingmotion by the traversing slide 41 "incooperation with the tapes 5D, the grinding wheel "l3 grinds one hank of one tooth to the correct involute shape sub'fiect to possible deviation from this shape at the tip or root of the tooth, "as described. During thisoperati'onthe point-of contact (Fig. 3) of the grinding wheel rim (i. e. where the latter contacts the tooth f-fiank' never moves in space; the wear "compensating device it-' lt-above described keeps it in the same place, namely on the hasecircle tangent or flin'e of c:- tion" rel-ans or 50, see'Fig.. ,3) a -l ittle to one side some long'ituiinal centrai plane '13 of the ma- B see Fig.2). When the other flank oi the tooth (or of another tooth) is to be ground, the turntable '6 is rotated through about about the "axis A, thereby inverting the {tool holder 1 and pivoting the-grinding wheel 13 through the same-angle. For this purpose the worm gear -8 is operated and the rotary movement is limited by engagement "of an adjustable screw stop 2"! with one of-two a'butments ii-8 provided on the slide 5 (Figs. 2a andh). In the present embodiment the axis is contained in the plane of the working rim of the grinding wheel 1'3 (Fig, 4). It

is perpendicular to, "but does not intersect the grinding wheel axis which, in the operating position of "the grinding wheel, is located below the axis A. Upon inversion of the grinding wheel, as iius-t described, although "the latter then presents its operative rim to the opposite -tooth flanks, its point of "contact -P would, owing to'tl'i'e described relation' between the grinding-wheel axis and the axis A, be Wl-l above the base circle if it were not for the vertical sliding movement'of the holder #2 jointly with the slide l0 relatively to the turn table '6. the slide I 4) is inverted-by rotation of the 'turn ta-ble Wigso it drops by gravity relatively to the latter along the 'ball bea ring "guides II I. For this purpose, slide M is freely'movabl'e with respect to the turn-table 6, but is associated with two ad-j-ustalble stops one of which normally rests on an abutment provided by oneedge of a proieotion or boss a l on the turn table t to limit the downward movement of the slide H1. The stops 2 9 are in the form of nuts engaged on oppositely threaded portions or a spindle '3'2 by rotation of which both stops can be simultaneously-adjustedto occupy positions thereon appropriate to the positioning of the slide 1 0, andh'e'nce 0f the grinding-wheel, so that the pointer contact P' of the-latter comes to lie on the base circle of the gear being ground. The spindle '32 is mounted in the slide ill for rotation but secured against axial movement with respect thereto. 'Iip'on'rota tion of the turn-table 6 with the slide ID to invert the latter, the-other stop '29, previously lowermost, comes uppermost, and the slide m drops vertically until this other stop 2-9 rests on its associated abutment constituted by the other edge of the boss 3-1. In this way, the point of-contact P of the grinding wheel 13 which had momentarily been situated too high in relation to the work being ground, is brought down again to 'its previous position on the "line of action or tangent of the base circle of the gear being ground. In both positions the general plane of the grinding wheel forms the same angle with the vertical plane. In practice, it is usual to grind first all the tooth flanks facing in one direction, then' to invert the "grinding wheel in the manner inst-described and to grind an the tooth flanks facing in the opposite direction, no manual adjustment being normally necessary during these two grinding operations, as the indexing device above referred to automatically turns the work to present the next tooth to the grinding wheel when the grinding or one tooth is finished. The inversion of the grinding wheel is repeated when it is desired to grind again the toothfla-riks facing in the first direction, the citherst'op 29 then resumi-ng cooperation with its abutment on the boss After inversion, the grinding wheel rim must be niovedda'teraliy into- "conta'ct with a tooth hank, and this is done by the horizontal-adjustment of theslide S 'With respeet'tothe slide ,3. This ad- :iustment is oiPcourse also-gmade, when the machine is firstset forgrinding a particularv internal tionstfi and 31 (by which numerals thespindle itself will hereinafter be identified). which are engaged by nuts 38 and 39 mounted thereon for axial movement butsecured against rotation. The nuts 3B and 39 are adapted to act as stops limiting the axial movement of the spindle 36, 31 by engagement with abutments provided by projections on the slide 3, as .shownin Fig. 2. The spindle 36, 31 is connectedto the slide .5 in a manner preventing axial movement relatively thereto, so that the slide accompanies the spindle 3E, 31in any axial movement made by the latter relatively to the slide 3. The position of the stops 38 and 3S axially of the spindle 36, 3'1 can be adjusted by rotation of the latter, and the exact positioning of these stops and, hence, the amount of material to be removed during a pointer 49 on the spindle 36, 31 cooperating with referenceindicia on the slide 3 (Fig. 1a). The horizontal displacement of theslide 5 is .effected by axial movement or" the spindle 36, 37

relatively to the slide ,3 by means of fluid pressure in a cylinder 4! mounted on the slide 3. The fiuid pressure acts on a piston 42 connected to the spindle 36, 31. Movement of the piston 42 under fluid pressure thus displaces the spindle 3,5,31 horizontally and,;with it the slide 5 until for example, the stop 39 contacts its abutment as shown in Fig. 2a. At this moment, a further rise of the fluid'pressure acting on the piston is prevented by the openingof two automatic excess pressure reliefv valves is provided in the piston .42. It. is therefore in effect the hydraulic pressure thatkeeps the grinding wheel in operative contact with the work;

A dressing device M (Figs. la, 2a and l) is mountedon the tool holder for reciprocation with respect thereto. It carries a cutting diamond which, with the device; is adapted to-,be displaced parallel to the working surface of the grinding wheel inorder, to effect a lateral truing or dressing of the latter. This is usually done be.- tween grindingoperations, i. e. with the grinding wheel rim disengaged from the work. In order to be able to return the grinding wheel rapidly toits proper position in contact with the work on completion of a dressing operation, a manually operable knob 9 (Fig; 4) isprovided which is secured to the axle pin of the ratchet wheel 18 and whichcan be turned to drive the gearing I9, 20 and the spindle 2| so as to effect the I becomes unevenly worn in use it requires peripheral dressing (apart from the occasional lateral dressing by the device, above referred to), such peripheral dressing consisting in turning the grinding wheel down to a somewhat smaller diameter. For this purpose, a device in the form of .25 the ensuing grinding operation is determined by ries .anappropriate cutting to.o1.- After sucha turning down operation, the grinding wheel, now

of smallerdiameter than before, .must be raised again to .its. proper grinding position with its point of contactP. disposed on the line of action of the gear teeth being ground. This'is done by adjustment of the stops 29 already referred to so as to raise the slide it, and with it the toolholder, [2 and the grinding wheeL relatively to the turn tablefibylan amount corresponding to the reduction in diameter of the grinding wheel.

At thesame time it is necessary for the turning-down device 33 and the feeler device 16 to be advanced towards the centre ofthe grinding wheel so as to remain in engagement with the operative rim thereof. This is arranged to take place automatically upon adjustment of the stops 29 by means of the spindle 32. For this purpose the spindle 32 is coupled to another. screwthreaded spindle 34 by means of bevel gearing 35' (Figs. 1a and 2a,). The devices Hi and 33 and associated parts are carried by a mountingwhich, as can also be see'n from Fig. 4, has a bracket threadedly engaged by the spindle 34 so that rotation of the latter causes sliding movement of the mounting along apart of the slide iii to advance the devices l6 and 33 towards the grind ing wheel [3. Y Y

In general the adjustment by means of the stops 29 is used only'to alter the vertical setting of the grinding wheel in accordance with its diameter, whereasthe initial vertical adjustment of the grinding wheel to set its point of contact P on'a given gear base circle or line of action" is efiected by operation of the spindle a to raise or lower the slide 3, andwith it the whole grindin'gwheel mounting apparatus, along the stand- 'ard or frame}. This would be the normal adius'tment of the grinding wheel for work on gear wheels of diiferent diameters.

For the purpose of grinding internal gears with inclined (helical) teeth of invo-lute form on this machine, the standard 2 is pivoted about thevertical axis 1C (pivot 55) which passes through'thepoint oi intersection of the grinding wheel axis of rotation with the longitudinal central axis B of the machine. If the angle of inclination of the gear teeth (helixangle) is p, then the standard 2 is pivoted so that the plane of the grinding wheel-J forms an angle 6 with the axis B of the machine, i. e. with thedirection of forward movement of the work feed slide 48. Theiapparatus is shown in this position in Figs. 2 and 2a.

However, it is also necessary for the work to moveona helicalqpath instead of the straight forward 'feed towards the grinding wheel im-. parted to' it by the slide 48 parallel to the axis B of the machine. Such helical; path of each tooth flank being ground is of course necessary to ensure constantcontact of the helical tooth flank with the grinding wheel. The gear being ground must therefore undergo an additional rotary motionof magnitude dy==dx tan. ,8 measured at the base circle of the teeth being ground. For this purpose,- the frame 52, to which the ends of the steel tapes 50 fastened to the rolling are 49 are so.- cured by means of the levers 5|, is caused to be displaced transversely of the feed slide 48, on which itis mounted for such relative movement, sliding thereover on rollers 53 (Fig. 3). This transverse movement of the frame 52 is caused to take place simultaneously with the movement whereby the slide 48 is fed forward .towardsthe a lever 33 (Figs. 1c and l) is provided which car ,7; grinding tool, and; it will be understood that thereby an additional rotation is imparted to the rolling are 49 and to the gear wheel being ground, that is to say a rotation additional to. that'necessary for true rolling. motion. In order to bring about this transverse. movement of the frame 52; the latter has a pin 58 engaging in a guide groove or slot provided in a -member 59 'adjustably mounted on the machine bed I. The member 59' is adapted to be angula-rly adjusted by means of a worm gear drive 60' ('Fig. 2). If it is so adjusted that the guide slot forms an angle o'with the longitudinal central axis 13 of the machine (this being the position shown in Fig. 2) then the frame. 52 will be pulled laterally thereby as the feed slide 48. advances towards, the grindin tool, the ratio of this lateral movementto the forward feed being tan ,3. This lateral move-. ment is of course transmitted bythe steeltapes, 5.0V to the rolling are 49 and results in the correct, additional rotary motion being imparted tov the gear wheel being ground. so that. the tooth flank: in contact with the grinding wheel makes a. helical movement with respect to the stationary working point of the latter. By adjusting the guide groove in the machine bed to, 5:0", that is to say parallel to the direction of move ment or the feed slide Q8 (i. e. to the longitudinal central plane B of the. machine), there .is no 1jatoral. displacement. of the frame 52,, and the machine is ready' for grinding the. straight teeth of, ordinary internally toothed spur gear wheels.

The method of obtaining motive power for the movement of the parts described in the. foregoing has notv been thought worthy of special mention, as many such methods are well known and understood in the art, any of which can be applied to the machine above described.

While a preferred embodiment of this invention has been described in the foregoing, it will be appreciated by those skilled in the art'that many modifications may be made in, the details of construction, disposition and cooperative. at: rangements of the parts without departing from the spirit of the invention Whilh, therefore, is not to. be deemed to be limited by the foregoing description or otherwise than by the. scope; of the appended claims. v

What I claim, and desire to secure by Letters Patent. is f 1. Machine for grinding the tooth flanksof internally toothed gear wheels. comprising a triale grinding, wheel, a tool-holder on which said grinding wheel is mounted for rotation. driving means for rotating said grinding wheel, a workholder, driving means for imparting to said workholder a feed motion towards said; grinding wheel and simultaneously an involute generating roll- 118 motion with respect to said grinding wheel, a toolaholdersupporting structure on which said ool-holder is mounted for pivotal movement. about. a'pivotal axis disposed perpendicularly to, but not intersecting the axis of rotation of said. grinding wheel. and m ans. ior effecting sa d pivotal movement of said tool-holder to. locate said grinding wheel in positions. approximately 180 apart. with respect to said pivotal axis for grinding' one, flank of the teeth "or the. wor one. of said positions and the other flank in the; other of s id positions. g V

2. ,Machine for grinding the tooth flanks of internally toothed gear Wheels comprising a single rindin wheel hav n a a row active riin ad- .iacent the periphery thereof for making. sob

a tool-holder on which said grinding wheel is mounted for rotation, driving means for rotating said grinding wheel, a work-holder, driving means for imparting to said work-holder a feed motion towards said grinding wheel and simultaneously an involute generating rolling motion with re, spect to said. grinding wheel, a tool-holder supporting structure on which, said tool-holder is mounted for pivotal movement about. a pivotal axis disposed perpendicularly to, but not inter seating, the axis. of rotation of said nding.

wheel and for linear sliding movement ma plane perpendicular to said pivotalv axis, adjustable stop means for limiting said sliding. move ent of said tool-holder in both directions, said grinding wheel having one position determined by said. stop means, for grinding one. flank of the teeth of the work, means for efiecting said pivotal.

movement of said tool-holder through approxi mately to invert said grinding wheel from said position thereof and locate its working point beyond the fline of action, and means for auto-' matically effecting said sliding movement of said tool-holder-to move said grinding wheel linearly to another position, also determined by said step means, inwhich its working point is again 10- cated on the line of action, for grinding the other flank of the teeth of the work.

3;. Mach ne for grinding the tooth flanks of internally toothed gear wheels comprising a siii gle grinding wheel, a tool-holder on which said grinding wheel is mountedfor rotation, driv ing' means for rotating said grinding wheel, a; work-holder, driving means for imparting to said work-holder a feed motion towards saidgrinding wheel and simultaneously an involute generating' rolling motion with respect to said grinding wheel, a tool-holder supporting structure on whichsaidtool-holder is mounted for pivotal movement about a substantially horizontal piv" otal axis disposed above, and perpendicular to, the axis of rotation of said grinding wheel, and for linear sliding movement in a plane perpendicular to said piv'otalaxis, adjustable stop means for limiting said sliding movement of said toolholder inboth directions, said grind-ingwheel being adapted in one position thereof to grind one flan-k of the teeth of the work, mean for effecting said pivotal movement of said tool-holder through approximately 180 to invert said grinding wheel from said position thereof and locate said axis of rotation thereof above said pivotal axis, and means for automatically effecting said sliding movement of said, toolholder to lower said grinding wheel inverted to another position thereof and restore said axis of rotation thereof to the same level below said pivotal axis as; before said pivotalmovement, said grinding wheel being adapted, in said other position thereof, to grind the other flank of the. teeth.

4. Machine for grinding the tooth flanks of internally' toothed gear wheels comprising a Single' grinding wheel, a tool-holder on which said grinding wheel is mounted for rotation, driving means. for rotating said grinding wheel, a work-holder, driving means for imparting to said WQ-Ikrhfiidl a feed motiontowards said grinding whee rid simultaneously an. involute generating roll ng m ti w e e o said. grindin wheel; a tool-holder supporting structure including 8 supin porting member, a turn-table member mounted,

for rotation on said supporting member about a substantially horizontal pivotal axis disposed above, and perpendicularly to, the axis of rotation of said grinding wheel, a slide member mounted on said turn-table member for free gravitational linear sliding movement relatively thereto in a plane perpendicular to said pivotal axis, two adjustable stop means alternately effective for limiting said sliding movement of said slide member in either direction depending on the position to which said turn-table member has been rotated, said tool-holder being carried by said slide memher which, in one position thereof determined by one, of said stop means, locates said grinding wheel for grinding one flank of the teeth of the work, and means for rotating said turn-table member about said pivotal axis through approximately 180 to invert said slide member and cause it to be lowered by gravity to another position thereof determined by the other of said stop means, said slide member, when inverted in said other position thereof, locating said grinding wheel for grinding the other flank of the teeth of the work. r

5. Machine for grinding the tooth flanks of internally toothed gear wheels comprising a single grinding wheel, a tool-holder on which said grindin wheel is mounted for rotation, driving means for rotating said grinding wheel, a workholder, driving means for imparting to said workholder a feed motion towards said grinding wheel and simultaneously an involute generating rolling motion with respect to said grinding wheel, a tool-holder supporting structure including a supporting member, a turn-table member mounted forrotation-on said. supporting member about a substantially horizontal :pivotal axis disposed above, and perpendicularly to, the axis of rotation of said grinding wheel, a slide member mounted on said turn-table member for free gravitational linear sliding movement relatively thereto in a plane perpendicular to said pivotal axis, two adjustable stop means alternately effective for limiting said sliding movement of said slide memher in either direction depending on the position to which said turn-table member has been rotated, said tool-holder being mounted on said slide member for substantially horizontal sliding adjustment withrespect thereto in the direction of said grinding wheel axis of rotation, said slide member, when in one position thereof determined by one of said stop means, locating said grinding wheel for grinding one flank of the teeth of the work, means for rotating said turn-table member about said pivotal axis through approximately 180 to invert said slide member and cause it to be. lowered by gravity to another position thereof determined by the other of said stop means, said slide member, when inverted in said other posi tion thereof, locating said grinding wheel for grinding the other flank of the teeth of the work, a cutting device adjustably mounted on said toolholder supporting structure for dressing the periphery of said grinding wheel by reducing the diameter thereof, a feeler device adjustably mounted on said tool-holder supporting structure for sensing the position of said grinding wheel axially thereof relatively to the work and correspondingly causing said tool-holder to be automatically adjusted horizontally with respect to said slide member to move said grinding wheel axially thereof towards the work in compensation for wear of said grinding wheel, and means common to said stop means, said cutting device and said feeler device for adjusting both said stop means to determine said positions of said slide member in accordance with the diameter of said grinding wheel and for simultaneously adjusting the position of said cutting device and said fecler. devicetoremain in engagement with said grinding Wheel upon reduction of the diameter thereof.

6. Machine for grinding the tooth flanks of internally toothed gear wheels comprising a sin gle grinding wheel, a tool-holder on which said grinding wheel is mounted for rotation, driving means for rotating said grinding wheel, a work holder, driving means for imparting to said workho-lder a feed motion towards said grinding wheel and simultaneously an involute generating rolling motion with respect to said grinding Wheel, a tool" holder supporting structure including a support-. ing member, a turn-table member mounted for rotationonsaid supporting member about a substantially horizontal pivotal axis disposed above, and perpendicularly to, the axis of rotation of said grinding wheel, a slide member mounted on said turn-table member for free gravitational linear sliding movement relatively thereto in a plane perpendicular to said pivotal axis, two adjustable stopmeans alternately effective for limitin'g'said sliding movement of said slide member in either direction depending on the position'to which said turn-table member has been rotated, said tool-holder being mounted on said slide member for substantially horizontal sliding ad justment with respect thereto in the direction of said grinding wheel axis of rotation, said slide member when in one position thereof determined by one of said stop means, locating said grinding wheel for grinding one flank of the teeth of the work, means for rotating said turntable memberabout said pivotal axis through approximately to invert said slide member and cause it to be lowered by gravity to another position thereof 1 determined by the other of said stop means, said slide member, when inverted in said other position thereof, locating said grinding wheel for grinding the other flank of the teeth of the worl a device for dressing the periphery of said grindingwheel by reducing the diameter thereof, a device for dressing the side of said grinding wheel and a feeler device for sensing the position of said grinding wheel axially thereof relatively to'the work and correspondingly causing said toolholder to be automatically adjusted horizontally with respect to said slide member to move said grinding wheel axially thereof towards the work in compensation for wear of said grinding wheel, said dressing devices and said feeler device being mounted on said tool-holding supporting structure for rotation with said turn-table member about said pivotal axis.

7. Machine for grinding the tooth flanks of internally toothed gear wheels comprising a single grinding wheel, a tool-holder on which said grinding wheel is mounted for rotation, driving means for rotating said grinding wheel, a work-holder, driving means for imparting to said work-holder a feedmotion towards said grinding wheel and simultaneously an involute generating rolling motion with respect to said grinding wheel, a toolholder supporting structure including a support-F, ing member, a first slide member mounted on said supporting member for substantially horizontal sliding adjustment with respect thereto in the direction of the axis of rotation of said grinding wheel, a turn-table member mounted for rotation on said first slide member about a sub-' stantially horizontal pivotal axis disposed above,

amnesia and perpendicnlar'to, saidl-grindi'ngwheel axis of rotation, a. second slide member mounted on. said turn-table member for free gravitational. linear sliding movement relatively thereto in a plane perpendicular a said pivotal axis, two adjustable stop means alternately effective for limitingsaid sliding: movement of said second slide member in:,either direction depending, on the position to which said turn-table member has beenrotated, said tool-holder being carried by said second slide member which, in one position thereof determined by one of'said stop means, locates said grinding wheel for grinding one flank of the teeth of the work, means for rotating said turn-table member about said pivotal axis through approximately 180 to invert said second slide member and cause it to be lowered by gravity to another position thereof determined by the other of said stop means, said second slide member, when inverted in said other position thereof, locating said grinding wheel for grinding the other flank of the teeth of the work, and operating means for causing said sliding adjustment of said first slide member to move said grinding wheel axially thereof away from the work prior to said rotation of said turn-table member and towards the work after said rotation of said turn-table member and to determine the depth of material to be removed from the work by said grinding wheel.

8. Machine for grinding the tooth flanks of internally toothed gear wheels comprising a machine bed and work-supporting and tool-supporting structures mounted on said bed, said worksupporting structure including a feed slide mounted on said bed for movement longitudinally thereof towards said tool-supporting structure, a traversing slide mounted on said feed slide for reciprocating movement relatively thereto perpendicularly to the direction of movement of said feed slide, driving means for causing said movements of said feed slide and said traversing slide, a

frame mounted on said feed slide, a rolling arc rotatably mounted on said traversing slide upon an axis parallel to the direction of movement of said feed slide, flexible steel tapesstretched between, and secured to, said frame and the circumference of said rolling are so as to cause ro tation of the latter as it reciprooates with said traversing slide relatively to said frame, a workholder mounted 'on said traversing slide coaxially with, and coupled to, said rolling arc to move the work with true involute generating rolling motion to and fro past said tool-supporting structure, and said tool-supporting structure including a single grinding wheel having a narrow active rim adjacent the'perip-hery thereof for making substantially point contact with the work, the working point of said rim being in operation disposed on the line of action of the teeth of the work, a tool-holder on which said grinding wheel is mounted for rotation, driving means for rotating said grinding wheel, a supporting member carried by said bed and having said tool-holder mounted thereon for pivotal movement about a substantially horizontal pivotal axis disposed perpendicularly to, but not intersecting, the axis of rotation of said grinding wheel and for linear sliding movement in a plane perpendicular to said pivotal axis, adjustable stop means for limiting said sliding movement of said tool-holder in both directions, said grinding wheel having one position, determined by said stop means, for grinding one flank of the teeth of the work, means for effecting said pivotal movement of said tool-holder through approximately 180 to invert said grinding, wheetfrom said position thereof and lo data its; working point-beyondthe. line of: action,

and means for automatically effecting said: slid.--

9. Machine for grinding the tooth flanks of internally toothed helical gear wheels comprising a machine bed and work-supporting and toolsupporting structures mounted on said bed, said work-supporting structure including a feed slide mounted on said bed for movement longitudinally thereof towards said tool-supporting structure, a traversing slide mounted o said feed slide for reciprocating movement relatively thereto perpendicularly to the direction of movement of said feed slide, driving means for causing said movements of said feed slide and said traversing slide, a frame mounted on said feed slide for movement relatively thereto perpendicularly to the direction of movement thereof, a member adjustably secured to said bed and having a guide slot therein, means for adjusting said member so that said guide slot forms an angle with the direction of movement of said feed slide equal to the helix angle of the teeth of the work, a guide member on said frame engaging said guide slot to cause said frame to make said movement relatively to said feed slide as the latter moves forward to wards said tool-supporting structure, a'rolling are rotatably mounted on said traversing slide upon an axis parallel to the direction of movement of said feed slide, flexible steel tapes stretched between, and secured to, said frame and the circumference of said rolling are so as to cause rotation of the latter as it reciprocates with said traversing slide relatively to said frame, the combined movement of said rolling arc being true rolling motion plus an additional rotary motion which is a function of the helix angle of the teeth of the work, a work-holder mounted on said traversing slide coaxially with, and coupled to said rolling arc to move the work to and fro past said tool-supporting structure with the correct motion for generating involute helical gear teeth, and said tool-supporting structure including a single grinding wheel having a narrow active rim adjacent the periphery thereof for making substantially point contact with the work, the work-- ing point of said rim being in operation disposed on the line of action of the teeth of the work, a tool-holder on which said grinding wheel is mounted for rotation, driving means for rotating said grinding wheel, a supporting member carrying said tool-holder and being mounted on said bed for swivelling movement about a vertical axis to set the general plane of said grinding wheel at an angle to the direction of movement of said feed Slide equal to the helix angle of the teeth of the work, said tool-holder being mounted on said supporting member for pivotal movement about a substantially horizontal pivotal axis disposed perpendicularly to, but not intersecting, the axis of rotation of said grinding wheel and for linear sliding movement in a plane perpendicular to said pivotal axis, adjustable stop means for limiting said sliding movement of said tool-holder in both directions, said grinding wheel having one position determined by said stop means for grinding one flank of the teeth of the work, means for effecting said pivotal movement of said tool-holder through approximately to invert said grind- 15 I 16" ing wheel from said position thereof and locate REFERENCES CITED its Working pomt beyond the of and The following references are of record in the means for automatically effecting said sliding me of this patent: movement of said tool-holder to move said grinding wheel linearly to another position, also de- 5 UNITED STATES PATENTS termined by said stop means, in which its working Number Name Date point is again located on the line of action, for 1,252,478 Nayes J an. 8, 1913 grinding the other flank of the teeth of the work. 1,870,764 Aeppli Aug. 9, 1932 ALBERT AEPPLI. 2,319,582 Carroll May 18, 1943 

